Griff Running like a bag of sh*t

[Quinny]

The initial message was deleted from this topic on 17 October 2011 at 10:29

[GreenV8S]

Your diagnosis makes sense. After the stuff you've already done, I move on to an electrical check of the analogue sensors, could be a coolant temp sender making the ECU think it's stone cold. Also put a passive strobe in series with one of the plug leads, good way to eliminate a lot of variables on the ignition side. I don't know whether you'd spot a misfire in all that lot so check the header temperatures to see if any are running cold.

[starmist]

Hi Andy, long time no speak. How's things?

I have suffered similar problems myself before, and it turned out to be a duff rotor arm. This was obviously degrading the spark voltage (going to ground) and cuasing all of the symptoms you describe, plus lurching on light throttle / low revs.

Make sure all plugs are gapped properly and are working okay. With 8 cylinders, you can have one not firing, and you'd hardly notice it, believe it or not.

BTW, did you fit those heads you've got in your garage over the winter?

[dnb]

Coolant temperature sensor as said already or the fuel temperature sensor (both are temperature dependant resistors) Or it could be a lambda sensor.

[Guillotine]

does sound like ignition/timing to me.

[stesrg]

Quinny nice to see you are still lending a helping hand hope you can solve it as I know you like a challenge somewhat like myself BTW still have not seen you asking for some charity stickers
Ste..

>> Edited by stesrg on Monday 30th May 18:51

[GreenV8S]

Does it go back to normal again after it's cooled right down? If so I still think you've got a mixture problem. When you checked the coolant temp sender, did you check the resistance back at the ECU? If the sender itself is OK then the next most likely problem is a poor circuit back to the ECU, and as you know an open circuit corresponds to a very cold reading. Also check the fuel temp sender, because fuel gets thinner as it warms up so the ECU holds the injectors open for longer when it thinks the fuel is cold.

There are other faults which can throw the mixture out, but these two are the most obvious and easiest to check.

My experience of ignition faults is that a weak spark is generally most obvious at full throttle and high revs, and heat-related failure (coil, ignition amp etc) typically causes a total failure/severe misfire rather than just gradually getting rougher and rougher. The progressive nature of the problem makes me think fuelling.

[Ballistic Banana]

Mines just started doing the complete opposite, cold starting and its like a bag of nails once warm it flies.
Been to MA recently where it was all ok and improved no end might need to return though if i cant find the problem. Takes a good 10-15 goes just to get it started.

BB

[old64er]

Is the coil breaking down when it is hot?

[HarryW]

The fact that it runs better after fitting the repacement sender is good the only other query I'd have with that is did you reset the ECU after changing it . Not being the brightest of units it may be still trying to apply old lessons learnt, IFYSWIM. IMHE anything that feeds the ECU, be it base idle adjustments or AFM idle pot, the ECU needs to be reset to stop it getting confused.
The above is assuing there was only one fault, the next is assuming that there is more than one. The above cleared the cold running the fact now that it is playing up when hot could mean its back to the drawing board. Draw a line under the sensor change and start agian, looking at the normal hot running areas of leads, plug heat shields, coil etc IMHO.

Harry

[Boosted LS1]

Sounds like it's flooding to me. Is the pressure regulator ok and is the vac hose to it connected/undamaged.

Boosted.

[GreenV8S]

You get massive over-fuelling, which is better under heavy throttle and worse under light throttle.

[HarryW]

I thought the range of the standard regulator was 2.5 - 2.7 bar with and without the vac . I could (as usual ) be totally wrong on that count, worth asking the question though.

Harry

[HarryW]

Really silly one not mentioned yet, I think, have you checked the throttle pot .

Harry

Apologies if its been mentioned couldn't see it when reading back quickly just now.

[HarryW]

Quinny said:

..... Does anyone know when MA uses the rolling road in Shrewsbury? I've mailed him but not had a reply. ....... Andy.

If you mean Mech Repairs its normally on a Friday.

H

[GreenV8S]

HarryW said:

I thought the range of the standard regulator was 2.5 - 2.7 bar with and without the vac . I could (as usual ) be totally wrong on that count, worth asking the question though. Harry

There's a vac line from the plenum to the fuel pressure regulator. The fuel pressure is controlled relative to the manifold pressure not to atmospheric pressure. As you close the throttle and the manifold pressure drops, the fuel pressure drops. This way it maintains a constant differential pressure across the injectors.

[HarryW]

Quinny said:

HarryW said: If you mean Mech Repairs its normally on a Friday. No not Mech repairs Harry, I've spoken to Mark, he goes to a place called SAS in Shrewsbury (Shrewsbury Auto Services) only 20 miles from my house, so just need to fix up a convenient time now. Andy.

Ah well, I tried , at least its on the way to being sorted now .
Be interested to know what was wrong once Mark has waved his wand over it though.

Harry

[griffter]

Quinny said:

Thanks Harry, The funny thing is when I put all my ignition componenets on it, it did seem a bit better, but still wasn't right. I've put all the original parts back now apart from the coolant sensor cos that was definitly goosed, and true to form it's running like a bag of shite again. Andy.

Did you change/clean the plugs? They'll be fouled to b8ggery by now and won't help matters!

[stesrg]

Quinny said:

stesrg said: BTW still have not seen you asking for some charity stickers Ste.. What charity stickers are they Steve? I already give regularly to the Haemophilia society and to a local animal rescue place, but I'm a sucker for a good cause. Andy.

Hi andy see my posts STICKERS STICKERS 2 and Thanks STICKERS
Ste..

[GreenV8S]

I got a spare from fleabay for £80 (no you can't have it), they come up quite often. Are you sure you need to replace the whole thing? You don't often hear of mechanical failure, but surely it would be possible to replace the pickup, amplifier etc separately?